Flat hardboard panels of uniform density throughout have been made by a variety of wet and dry fiber processes. Some of these previously known wet and dry processes are disclosed in prior art U.S. Pat. No. 4,038,131. Hardboard panels produced by hot pressing a mat of dry fibers have some significantly different characteristics than hardboard panels produced by hot pressing wet or moist fibers. Typically, hardboard panels made by hot pressing wet fibers have a lower density, greater dimensional stability, less weight and a smooth outer face with substantially improved surface finish, lower rate of moisture and paint absorption and better weathering and painting characteristics.
A lapped siding panel of uniform density and a method of making this panel are disclosed in U.S. Pat. Nos. 4,726,881 and 4,622,190. The front and back faces of :his hardboard panel have essentially the same profile and are formed by hot pressing a wet fiber mat between a pair of plates having juxtaposed faces with complimentary contours. To permit moisture to escape, the wet mat is hot pressed on an underlying wire screen which is plastically deformed by the pressing so that it substantially follows the contour of the lower plate. When the press is opened, the formed panel is released from the lower press plate and the screen by tensioning the screen sufficiently to flatten or straighten it out. In the next hot pressing of another wet fiber mat the screen is again plastically deformed to conform to the contour of the lower plate. This repeated deforming and straightening of the wire screen is believed to cause it to rapidly deteriorate and break so that frequently it must be replaced with another screen.